1. Field of the Invention
The invention relates to a tire module which is installed on the inside of a tire, in particular of a vehicle tire, to a tire monitoring system and to a method for protecting the tire module.
The invention is suitable in particular for acquiring tire state variables with a system which is autonomous in terms of energy.
2. Description of the Related Art
In modern motor vehicles, pneumatic tire pressure-sensing devices are increasingly being used to avoid defects or accidents which are due to an excessively low tire air pressure. In many of these systems, a tire module is arranged respectively on each wheel, in particular in the interior of the tire. A tire module often comprises at least one sensor for sensing at least one tire parameter, in particular the tire pressure, and a transmitter unit and, if appropriate, electronic evaluation system. The energy supply of the electronic components can be provided, for example, by a battery, a microgenerator with a piezoelectric element or a transponder coil.
DE 44 02 136 A1 discloses a system for determining the operating parameters of vehicle tires, in which system a sensor unit, an electronic evaluation system and a piezoelectric element, which supplies the other system components with energy, are arranged on a carrier body. The piezoelectric element has a multi-layer design.
DE 10 2004 046 193 A1 describes a pressure sensor for the wireless measurement of pressure in a tire, and an associated antenna device for transmitting and receiving electromagnetic fields.
DE 10 2006 003 825 A1 discloses a batteryless tire pressure-monitoring system which senses tire parameters via a sensor, wherein the sensor is connected on the input end to an antenna in order to receive a modulated microwave signal and in order to convert part of the modulated microwave signal into a supply voltage via a control circuit.
EP 1 614 552 A1 discloses a bridge-shaped patch with an electromechanical converter for use in a vehicle tire.
DE 10 2004 031 810 A1 specifies a tire monitoring system which generates electrical energy by means of a piezoelectric element which is arranged inside the tire.
DE 43 29 591 C2 discloses a device for monitoring the tire air pressure which receives an electrical pulse via a sensor the degree of deformation of the tire as it passes through the contact area, and an evaluation unit identifies the degree of deformation.
DE 103 29 700 A1 describes a method which identifies the wheel load and the tire air pressure from the rotational speed of the tire and from the length of the contact area and the deformation by means of a differentiating sensor.
DE 10 2004 001 250 B4 discloses a device which determines the lateral positions of the wheels from the deformation of the tire as it passes through the contact area in bends by means of sensor units.
When a microgenerator is used to supply energy to a tire module which is installed in the interior of a tire, it is necessary to ensure that the microgenerator is configured in such a way that it at least withstands the loading during the entire service life of the tire. In this context it is advantageous if the microgenerator forms a compact module with the other components such as, for example, the pieces of equipment.